There are a number of bottle capping machines currently used to apply screw caps onto bottles. In general such machines employ a reciprocating mechanism to reciprocate a screw cap applying spindle assembly through a capping cycle. A screw cap chuck, typically constructed of a tool grade steel, is attached to the spindle. These machines operate at a predetermined downward stroke while applying a pre-determined torque to the screw cap. The operating height of the chuck is usually adjustable to allow for various bottle heights. An example of such an apparatus is shown in U.S. Pat. No. 3,031,822 issued May 1, 1962, in the name of George H. Dimond entitled Chuck for Capping Machines. The basic design shown by this patent is still in use today in capping machines made by Figgie International Inc.
The primary elements of the screw-on capping chuck, of the type first described in U.S. Pat. No. 3,031,822, are chuck jaws, jaw bell, a stripper, and a stem. The jaws are retained in the bell by the stem which is associated with a torque trigger through a spring coupling. An adaptor connects the chuck to a spindle sleeve and transmits the rotary motion of the spindle sleeve to the torque trigger. A push rod extends through the sleeve and is adapted to actuate the stripper. The chuck jaws are opened by reciprocal movement of the spindle sleeve upward forcing the stripper between the chuck jaws. The cap is then picked up by reciprocal movement of the spindle sleeve downward onto the cap which displaces the stripper, snapping the jaws closed. The cap is then screwed onto the container. Opening of the jaws to release the capped container is accomplished by the torque opening feature of the torque trigger.
The torque trigger is provided with two flat rectangular lugs that rest in stair-like slots carved into the sleeve of the jaw bell. The torque trigger is, through moving closer to the bell via the force of the spring, adapted to actuate the stripper to open the jaws a sufficient amount to release the capped container.
In the chuck's rest position, the torque trigger is positioned in the lower slot of the bell's collar and due to the torque in the spring is forced against the back of the slot. The stripper is forced into the jaws by the trigger and spring. In operation, the unit is first "reset" whereby the chuck is reciprocated back against the push rod which forces the stripper fully down between the chuck jaws. At the same time the stem and bell are forced down relative to the torque trigger which allows the lugs to rotate up to the next stair step in the slot via the torque in the spring. At this point the stripper is fully wedged between the jaws and held in place by the pressure of the jaws. The chuck is then reciprocated downward to pick up a cap. The cap displaces the stripper upward into the bell, at which point the jaws snap shut via the action of the spring acting against the stem. At this point the stripper rides freely atop the cap and the torque trigger is still positioned on the upper platform of the bell sleeve. The chuck is then brought over the container to which the cap is to be affixed and is reciprocated down onto the container.
When the resistance between the cap and the container overcomes the torque of the spring, the jaws cease rotating, which causes the stem and bell to stop rotating. The torque trigger continues its rotation against the torque of the spring, causing the lug to move into the lower slot, which forces the stripper to push the jaws apart, freeing the cap. The chuck is now in the rest position and ready for another cycle.
To adjust the torque in the chuck, it must first be removed from the adaptor sleeve and the spring either wound or unwound to increase or decrease the amount of resistance needed to overcome the torque in the spring.
There are a number of applications for machines of this type where high speeds and precise torque are required. For example, the pharmaceutical industry makes extensive use of these machines when packaging chemicals for distribution. However, due to the nature of the coupling between the spring and the stem it has been impossible to visually set a chuck for a certain torque. Rather, each chuck must be individually tested and adjusted prior to use. Likewise, each chuck must be tested and set when adjustments need to be made. Further, chucks made in accordance with the prior art are also limited in the size caps they can apply, due to the tendency of the lugs to shear off when subjected to high torque when resetting after applying large caps such as to laundry detergent bottles which require that the spring be tightly wound.